1. Field of the Invention
This invention relates generally to storage networks and, more specifically, to a network device that generates a synthetic namespace to customize directories in a decentralized storage network.
2. Description of Related Art
In a computer network, NAS (Network Attached Storage) file servers connected directly to the network provide an inexpensive and easily configurable solution for a storage network. These NAS file servers are self-sufficient because they contain file systems that allow interoperability with clients running any operating system and communication using open protocols. For example, a Unix-based client can use the NFS (Network File System) protocol by Sun Microsystems, Inc. of Santa Clara, Calif. and a Windows-based client can use CIFS (Common Internet File System) by Microsoft Corp. of Redmond, Wash. to access files on a NAS file server. However, the operating system does not affect communication between the client and file server. Thus, NAS file servers provide true universal file access.
By contrast, more expensive and powerful SAN (Storage Area Network) file servers use resources connected by Fibre Channel on a back-end, or a dedicated network. A SAN file system is part of the operating system or an application running on the client. But heterogeneous client operating systems may require additional copies of each file to be stored on the storage network to ensure compatibility on the SAN file server. Additionally, communication between file servers on a SAN use proprietary protocols and thus are typically provided by a common vendor. As a result, NAS file servers are preferred when price and ease of use are major considerations. However, the differences between NAS storage networks and SAN storage networks also have drawbacks.
One drawback with NAS file servers is that there is no centralized control. Accordingly, each client must maintain communication channels to each of the NAS file servers separately. When NAS file servers are either added or removed from the storage network, each client must mount or unmount directories for the associated storage resources as appropriate. This is particularly inefficient when there are changes in hardware, but not in the particular files available on the network, such as when a failing NAS file server is replaced with an identically configured back-up NAS file server.
A related drawback is that a client must be reconfigured each time a file is relocated within the storage network, such as during file migration or file replication. The client generates a NAS file handle that identifies a physical location of the directory or file object on the file server using a file handle or path name. To access the object, the client sends an object access request directly to the NAS file server. When the file is relocated to a different NAS file server, a new file handle is required.
An additional drawback with NAS file servers is that mounted directories are typically tied to the physical share. Different physical shares can be on different file servers. When mounted, the client views a namespace of the physical share to find a file or directory, and is limited to that particular physical share. However, related files and directories can be spread across different physical shares. In addition, an administrator may want to limit access or permissions of users within the physical shares.
Therefore, what is needed is a network device to customize a namespace with a synthetic namespace. Furthermore, the namespace should provide, for example, a per user or per location customization.